( 386 ) 



LIT K i; A T U l\ K: 



I. (Ir.sii.NV iiiul MA'riiiKWs, .Iduiiial of pliysioloirx . Vol. XXI. 



i>. H. K. HKKiN(i, I'lliii^'oi's Arcliiv. lid. l.XXXll. 



){. J. Mackenzik, JdUiiiJil of I'jiliiology and l!a(U'iioloi:'\ . Vul. II. 



1. K. F. Wi:m:ki;ba(:ii, Zeitscluifl iiir Klin. iMcilicin. lk\. XXXVI. 



I). 'I'll. W. E.\GKL.MANN, Sur la lraii.snii(?sion ri'ci|)i()(|iic cl in(Jcipro(|iic'. Aicliivcs Nócr- 

 landaiscs XXX. 



(1. Til. \V, ]v\iiKi,.MA.\.\,. "(Jndorzui'kiiigcn" i'liysiul. lahofat. Ulrcchl. IV Scries. Ill 

 Vol. 18'»5. 



Mathematics. "(hi the ijvoniclfird} ri'in-i'st'iihitioii of the ind/iini 



(if ri(i-l<il>l(' si/strnis" . Ilv Pi'of. .1. ('ardinaal. 



1. In Iwo coiimiiiiiicalioiis ' ) sdiiic llicorciiis June Ix^cii (Icxclojtcd 

 lt\' inc. rclnlinii' <<> IIk' motion of \ .iriahlc svslcins. Also in lliis siih- 

 (livisioii of llic doclrim' ol" niolion llic niclliod of llic uconieliMcal 

 i-cprcscnlalion occiirrinii- ^^ IV('(|n('nllv in Malhcinalics can he applied. 

 Tlic follow inu' coniinnnicalion lias in \ icw lo incnlioii sonic parli- 

 cidars on (liis snhjccl. Tlic rcprcscnialion in (jiicsiion is Ircalcd ") 

 1)\ \l. Stiijm. b'roni Uiis Ircalisc 1 dcrixc llic sliorl siiiiiniar\ . wliicdi 

 niiisl needs a])|K'ar here as an inlrodiielion lo llic snltject. 



'l. In llic (|iiolc<| considci-alions Iwo coinplcxes of ravs plavc*! 

 an ini|>orlanl |»arl, nainclv llic Iclraliedral complex lornicd l>v lli(> 

 dii-cctions of llic xclocilics of llic poiiils of llic moxinu- s_\>leiii and 

 the i-a\s of a focal svslcin hclonuiiiu' to it: the latter consisis lor 

 the molioii of an inxarialtlc svslcin of the normals of the trajeclorics 

 of the points and for a projcctiNcI v \arialtle system of I'avs whose 

 conslrnclion t(»ok a ureal part of the considerations. The pin-pose 

 mnsi he to oltlain a simnllaneoiis n^prcscntation of complex and focal 

 sNstein ; it will prox'c dcsirahlc to uixc the foremost place lo the 

 rcpr(>sentation of the focal svsicm. 



.">. Let thus he L!,i\-cn the focal svslem A sitiiatc(l in the^pace^i'. 

 Accordini!: lo ihc mclhod of Svia I':stI'',|{ let lis suppose twd planes 

 ^ and > with two projectix'c pencils of ravs sitiiatc(| in them with 

 their N'crtices A' and ,\ silnalcd on the line (d" iiitersccti(»n ^^' ./'. 



') I'rocfcdiiiLis of llif Koii. Akad. van \\'('l('ii.sc!i., scdioii of science, vol. IV, 

 pact's 48!) and 088. 



") Die Gebilde ersleii uiid zweileu Grades dcr Liniengeomelrie, I, p. !2ü7. 



